package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;
    @Resource
    private CacheClient cacheClient;

    @Override
    public Object queryById(Long id) {
        //缓存穿透
//        Shop shop = cacheClient
//                .queryWithPassThrough(CACHE_SHOP_KEY, id, Shop.class, this::getById,CACHE_SHOP_TTL,TimeUnit.MINUTES);

        //互斥锁解决缓存击穿
        //Shop shop = queryWithMutex(id);

        //逻辑过期解决缓存穿透
        Shop shop = cacheClient
                .queryWithLogicalExpire(CACHE_SHOP_KEY, id, Shop.class, this::getById,CACHE_SHOP_TTL,TimeUnit.MINUTES);
        if (shop == null) {
            return Result.fail("店铺不存在");
        }
        return Result.ok(shop);
    }

    //互斥锁解决缓存击穿
    public Shop queryWithMutex(Long id) {
        String key = CACHE_SHOP_KEY + id;
        //1.redis中查询
        String shopJSON = stringRedisTemplate.opsForValue().get(key);
        //2.存在就返回
        if(StrUtil.isNotBlank(shopJSON)){
            Shop shop = JSONUtil.toBean(shopJSON, Shop.class);
            return shop;
        }
        //判断是否为空字符串
        if (shopJSON !=null){
            return null;
        }
        //3.建立缓存重建
        String lockKey = LOCK_SHOP_KEY + id;
        Shop shop = null;
        try {
            //3.1尝试获取所
            boolean isLock = tryLock(lockKey);
            if(!isLock) {
                //2.2获取失败，休眠后重新查询
                Thread.sleep(50);
                return queryWithMutex(id);
            }
            //3.2获取成功，缓存重建
            shop = getById(id);
            //4.不存在，返回错误信息
            if(shop == null){
                stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
                return null;
            }
            //5.存在，将数据写入redis缓存并返回数据
            stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            //6. 释放锁
            unlock(lockKey);
        }
        return shop;
    }
    //缓存穿透方法封装
    public Shop queryWithPassThrough(Long id) {
        String key = CACHE_SHOP_KEY + id;
        //1.redis中查询
        String shopJSON = stringRedisTemplate.opsForValue().get(key);
        //2.存在就返回
        if(StrUtil.isNotBlank(shopJSON)){
            Shop shop = JSONUtil.toBean(shopJSON, Shop.class);
            return shop;
        }
        //判断是否为空字符串
        if (shopJSON !=null){
            return null;
        }
        //3.不存在，从数据库中查询
        Shop shop = getById(id);
        //4.不存在，返回错误信息
        if(shop == null){
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //5.存在，将数据写入redis缓存并返回数据
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
        return shop;
    }
    //逻辑过期解决缓存穿透
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    public Shop queryWithLogicalExpire(Long id) {
        String key = CACHE_SHOP_KEY + id;
        //1.redis中查询
        String shopJSON = stringRedisTemplate.opsForValue().get(key);
        //2.不存在，返回null
        if(StrUtil.isBlank(shopJSON)){
            return null;
        }
        //3.命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJSON, RedisData.class);
        Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(), Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //4.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //4.1未过期，直接返回店铺信息
            return shop;
        }
        //4.2已过期，需要缓存重建
        //5.缓存重建
        //5.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //5.2判断是否获取锁成功
        if(isLock){
            //5.3成功，开启独立线程，实现缓存重建
            if (expireTime.isAfter(LocalDateTime.now())) {
                //再次检测redis缓存是否过期，未过期，直接返回店铺信息
                return shop;
            }
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //重建缓存
                    this.saveShop2Redis(1L,3600L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }
        //6.4失败，返回过期的商品信息
        return shop;
    }

    //尝试获取锁
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    //释放锁
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }


    //预存逻辑过期时间
    public void saveShop2Redis(Long id, Long expireSeconds){
        //1.查询店铺数据
        Shop shop = getById(id);
        //2.封装过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //3.写入redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY+id,JSONUtil.toJsonStr(redisData));
    }

    //商铺数据更新
    @Override
    @Transactional
    public Result update(Shop shop) {

        Long id = shop.getId();
        if (id == null) {
            return Result.fail("店铺ID不能为空");
        }
        //1.更新数据库
        updateById(shop);
        //2.删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);
        return Result.ok();
    }
}
